public removeClicker(id: string): void {

    // remove clicker from the service
    this.clickers = this.clickers.filter((clicker: Clicker) => { return clicker.getId() !== id; });

    // remove from ids array
    this.ids = this.ids.filter((filterId: string) => { return filterId !== id; });

    // null id in db
    this.storage.remove(id);

    // update service's ids array
    this.storage.set('ids', JSON.stringify(this.ids));
  }

  public newClicker(name: string): string {
    const id: string = this.uid();
    const clicker: Clicker = new Clicker(id, name);

    // add the clicker to the service
    this.clickers.push(clicker);
    // add the id to the service (need to keep a separate reference of IDs so we can cold load clickers)
    this.ids.push(id);
    // save the clicker by id
    this.storage.set(id, JSON.stringify(clicker));
    // save the service's ids array
    this.storage.set('ids', JSON.stringify(this.ids));

    return id;
  }

 return new Promise((resolve: Function) => {
   let ids: Array<string> = [];
   this.storage.get('ids') // return the promise so we can chain initClickers
     .then((rawIds: string) => {
       // ids are stored as stringified JSON array
       ids = JSON.parse(rawIds) || [];
     })
     .then(() => resolve(ids));
 });

 return new Promise((resolve: Function) => {
   let clickers: Array<Clicker> = [];
   for (let id of ids) {
     this.storage.get(id)
       .then((clicker: string) => {
         clickers.push(this.initClicker(clicker));
       });
   }
   resolve(clickers);
 });

 public doClick(id: string): void {
   const clicker: Clicker = this.getClicker(id);
   clicker.doClick();
   // save the clicker with updated click in storage
   this.storage.set(clicker.getId(), JSON.stringify(clicker));
 }

 public remove(key: string): Promise<{}> {
   return this.storage.remove(key);
 }

 public set(key: string, value: string): Promise<{}> {
   return this.storage.set(key, value);
 }

 public get(key: string): Promise<{}> {
   return this.storage.get(key);
 }